1. Field of the Invention
The present invention relates generally to equipment used in semiconductor processing. More particularly, the present invention relates to a configuration for magnets and/or coils of a planar motor that allows two stages of an overall stage apparatus to operate close together.
2. Description of the Related Art
Many stage apparatus include stages which would benefit from operating in close proximity to each other. For example, in a lithography system such as an immersion lithography system, the ability for two stages, as for example two wafer stages or a wafer stage and a measurement stage, to operate in close proximity to each other enhances the performance of the system.
Stages that are part of a lithography system, e.g., moving magnet stages, generally utilize linear or planar motors to drive the stages. A linear or planar motor typically includes a mover and a stator, one of which contains an array of coils and the other of which contains an array of permanent magnets. “Moving coil” generally refers to motors where the mover contains the coil array and the stator contains the magnet array. “Moving magnet” generally refers to motors where the stator contains the coil array and the mover contains the magnet array. In a stage driven by a moving magnet planar motor, magnets mounted on the stage may be oriented such that some magnets, e.g., X magnets, of a substantially continuous array are oriented to create a force in at least an X direction, and other magnets, e.g., Y magnets, of the array are oriented to create a force in at least a Y direction. A stator may include some coils oriented to produce force in at least an X direction, e.g., X coils, and other coils oriented to produce force in at least a Y direction, e.g., Y coils. The magnets and the stator are generally effective in generating desired forces, e.g., a desired force in an X direction may be generated when an appropriate X magnet interacts with an X coil, additional forces, normally of a smaller magnitude, that are not desired may also be generated.
When two stages of a lithography system are relatively close to one another, while a desired force may be generated to drive one stage, undesired forces may also be generated that have an adverse effect on the other stage. In other words, when two stages are driven by a moving magnet planar motor system, in generating a desired force to drive one stage, disturbance forces that have a relatively significant adverse effect on the other stage may be created. To avoid generating such disturbance forces, the two stages may be spaced further apart, thereby impacting the ability for the two stages to operate close together.